Described herein a method of manufacturing a metal shape that includes contacting a liquid metal and a surface of a foundry core under conditions wherein vein defects occur, the surface of the foundry core comprising a foundry aggregate, a combustible-organic material and a polyurethane resin, and the surface of the foundry core being free of or essentially free of an anti-veining agent; cooling the liquid metal to a temperature below its melting point thereby forming a metal shape; and then removing the foundry core from the metal shape.